In general, 2-dimension beamforming (2D-BF) means having the transmission/reception radio beam(s) formed at different azimuth(s). Though the beam(s) might be of multiple azimuths to same receiver (multi-path) or different receivers (MU), in elevation angle, the beams have a same degree of departure (DoD) or Degree of arrival (DoA).
In contrast, so-called 3-dimension (3D)-BF will direct the beams to certain DoDs or receive the beams from certain DoAs in both azimuth and elevation angles. This might be advantageous where the multiple paths exhibit a wide angle-spread of DoDs or DoAs in elevation so that this characteristic could be exploited to synthesize the transmission signals or analyze the reception signals in the elevation dimension.
The realistic radio propagation and geographic distribution of the transmitters and receivers are truly 3D, diverse, and time-varying. For example, FIG. 1 illustrates current non-uniformality reality of UEs distribution. UEs distribution may vary with the time of a day. Typically, during daytime, people gather in the central business districts while at night time, they come back home in the residential area. UEs' distribution may also relate to different landscape of regions, such as downtown or suburb, etc. Usually, UEs are distributed and clustered in a 3D domain 10 which contains adjacent cells 11, base stations 12, buildings 13 and individual UEs 15; arrows indicate the radio wave radiated by the base station; and UEs' height and azimuth distributions are time-varying and influential to system performance. Therefore, the new generation transceiver and antenna array design has to be of 3D features and dynamic.
However, most of the signals processing methodologies so far are designed separately from the configuration of antenna characteristics, or vice-versa. This can not well adapt to the 3-Dimension and time-varying characteristic of the UEs distribution in the real world, and thus might limit the further efficiency improvement of communications.
The existing planar antenna array has a potential to serve a 3D BF with a refinement. They may need certain RF connection modification or advanced dimension-reduction baseband circuitry network.